Incremental[=By_Area or Complete]
    Noincremental

    Determines the extent of the backup operation to be performed.
    The four possible options are:

    o  Noincremental

       If you do not specify any of the possible Incremental
       qualifier options, the default is the Noincremental qualifier.
       With the Noincremental qualifier, a full backup operation is
       performed on the database.

    o  Incremental

       If you specify the Incremental qualifier, an incremental
       backup of all the storage areas that have changed since the
       last full and complete backup operation on the database is
       performed.

    o  Incremental=By_Area

       If you specify the Incremental=By_Area qualifier, an
       incremental backup operation is performed. The Incremental=By_
       Area qualifier backs up those database pages that have
       changed in each selected storage area since the last full
       backup operation was performed on the area. The last full
       backup operation performed on the area is the later of the
       following:

       -  The last full and complete backup operation performed on
          the database

       -  The last full by-area backup operation performed on the
          area

       With an incremental by-area backup operation, each storage
       area backed up might contain changes for a different time
       interval, which can make restoring multiple storage areas more
       complex.

    o  Incremental=Complete

       If you specify the Incremental=Complete qualifier, an
       incremental backup operation on all of the storage areas
       that have changed since the last full and complete backup
       operation on the database is performed. Selecting the
       Incremental=Complete qualifier is the same as selecting the
       Incremental qualifier.

    Following a full database backup operation, each subsequent
    incremental backup operation replaces all previous incremental
    backup operations.

    The following two messages are meant to provide an aid for
    designing more effective backup strategies. They are printed
    as part of the per-area summary statistics, and they provide a
    guide to the incremental benefit of the incremental operation:

    o  "Est. cost to backup relative to a full backup is x.yy"

    o  "Est. cost to restore relative to a full restore is x.yy"

    These estimates are only approximate and reflect the disk
    input/output (I/O) cost for the backup or restore operations
    of that area. Tape I/O, CPU, and all other costs are ignored.
    The disk I/O costs take into account the number of I/O operations
    needed and the requirement for a disk head seek to perform the
    I/O. Each disk type has its own relative costs-transfer rate,
    latency, seek time-and the cost of a given sequence of I/Os is
    also affected by competition for the disk by other processes.
    Consequently, the estimates do not translate directly into "clock
    time." But they should nevertheless be useful for determining
    the point at which the incremental operation is becoming less
    productive.

    The relative costs can vary widely, and can be much higher than
    1.00. The actual cost depends on the number and location of the
    pages backed up. An incremental restore operation must always
    follow a full restore operation, so the actual estimate of
    restoring the area is actually 1.00 higher than reported when
    that full restore operation is accounted for. The guideline that
    Oracle Corporation recommends is, "Perform full backup operations
    when the estimated cost of a restore operation approaches 2.00."